This classic Pilates exercise strengthens the core and inner thighs.
How to do it: Lie faceup with your knees and hips bent 90 degrees, hands by your side. Lift your head, shoulders, and upper back off the ground, and begin to pulse your arms, taking long, deep breaths (inhale for 10 counts, exhale for 10 counts). Your core should be engaged the entire time so that everything but your arms stays completely still. Continue taking deep breaths until you get to 100 arms pulses.